1. Field of the Invention
The present invention generally relates to clamping apparatus used to removeably clamp documents or other like articles and, more particularly, to those clamping apparatus which include means for providing visual tabs or indicia.
2. Prior Art
The prior art exhibits a number of devices which are conventionally described as paper clips or visual tabs which are used to clamp together papers, documents or other like objects as well as act as visual signals. The primary feature which must be exhibited by all clipping devices is the ability to provide an adequate clamping force without damaging the documents or the structure of the clip itself. Another difficulty with the fabrication of an adequate clipping device is the ability to clamp a pad of sheets which may comprise more than an insignificant number. The clamping devices disclosed by the prior art typically require that the number of sheets be sufficiently small for the pad to bend between the inner and outer clamping limbs of the clip. If the clip is used on a pad of sheets which is excessively thick, the free ends of the clamp stand off from the pad of sheets thereby raising the possibility that the clipping device will slide off of the sheets.
A specific type of clip which is disclosed by the prior art for clamping thicker documents is generally referred to as a butterfly clip. Butterfly clips are relatively complicated structures made from steel or wire and have two intercrossing clamping portions which grip the pad of sheets from both sides. These clips are expensive, susceptible to corrosion and, owing to their sharp ends, tend to damage the documents. Furthermore, they are extremely disadvantageous because of their shape and size when same are sought to be used in the mail.
The prior art discloses a number of clamping devices which are fabricated from injection molded plastic. The devices take a number of shapes, but typically all utilize a common structure. In one case, a substantially triangular outer clamping limb is utilized, one side of the triangle being open, each of the sections of the open side depending into inner clamping limbs which are parallel to each other and which are joined at a point within the triangle of the outer clamping limb. The common portion of the inner clamping limb flares outwardly into a pair of arms which are substantially parallel to the remaining two sections of the outer clamping limb. By fabricating the inner clamping limb with the pair of parallel members joined at the end thereof, this clip seeks to provide more flexibility at the point where the inner clamping limb joins the outer clamp. The deficiency of this device arises out of the inability to apply an adequate clamping force to the document being bound. This fully defeats the primary objective of the clamping structure, i.e., being capable of holding a thick pad of sheets while simultaneously applying an adequate clamping force.
Another device disclosed by the prior art utilizes a pair of substantially U-shaped clamping members which are interconnected by cross-portions to form an endless strand. As with the base of the clip described hereinabove, the structure seeks to add resiliency by including an opening within the inner clamping arm. The inadequacy of the structure is created by precisely the elements which are added to provide resiliency. By adding resiliency to the inner arm, the ability to provide adequate clamping strength is reduced.
The present invention substantially overcomes the deficiencies which are exhibited by the devices disclosed by the prior art. A substantially V-shaped outer clamping limb is joined to a base portion at the opening of the outer limb, the profile of the outer clamping limb providing strength to the structure. An inner clamping arm depends centrally into the opening of the outer clamping limb, the profile of the inner clamping arm combining strength and resiliency. To provide the ability to clamp thick pads of sheets, a pair of concave indentations lie adjacent to and on opposite sides of the inner clamping arm. The weakening of the base portion adjacent the inner clamping arm provides that resiliency to the inner clamping arm which is necessary to permit the separation necessary to clamp a thick pad of sheets. To increase the utility of the present invention, the base portion incorporates a lattice of perpendicular ridges which produce a surface which can be discolored by pencil, ink or other marking devices.